Knowledge Base Article

How do I update the multicast hash table of the Triple Speed Ethernet IP core?

Description

As an example, assume you want the IP core to accept packets with a destination address of 01-1C-23-17-4A-CB. The IP core represents these address bits [47:0] in reverse order as shown below.

Address bits  7:0  = 0x01 -> Hash Code bit 0 (XOR MAC address 7:0)   = “1”
Address bits 15:8  = 0x1C -> Hash Code bit 1 (XOR MAC address 15:8)  = “1”
Address bits 23:16 = 0x23 -> Hash Code bit 2 (XOR MAC address 23:16) = “1”
Address bits 31:24 = 0x17 -> Hash Code bit 3 (XOR MAC address 31:24) = “0”
Address bits 39:32 = 0x4A -> Hash Code bit 4 (XOR MAC address 39:32) = “1”
Address bits 47:40 = 0xCB -> Hash Code bit 5 (XOR MAC address 47:40) = “1”

Therefore the hash code for this example is 0x37. To accept packets with this address, set bit 0 of the MultiCast Hash Table configuration register at "DWord offset" 0x77 (0x40 0x37) to the value of 1.

Updated 3 months ago
Version 2.0
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